code: def test_abs_difference(
      data: np.ndarray, params: dict, expected: Union[float, dict, bool]
  ):
      out = abs_difference(a=data["a"], b=data["b"])
      assert round(out, 2) == expected, "Test failed."
  
imports: import pytest
  from pytest_lazyfixture import lazy_fixture
  from quantus.functions.loss_func import mse
  from quantus.functions.similarity_func import *
label_desc: Use image node_id 20 for calling a global function with example usage: test_abs_difference(data, params, expected) without return types